Piezoelectric elements are used as sensors, actuators, and energy harvesting devices. Vibration or strain in a workpiece can be sensed from the electricity the piezoelectric element produces. That electricity can also be harvested to provide power for such things as charging a capacitor, recharging a battery, powering an electronic circuit, logging data from a sensor, or transmitting that data.
Alternatively, electricity from an external source can be provided to the piezoelectric element causing it to strain or vibrate. If mounted on a substrate this strain or vibration can be transferred to the substrate. The external source can include a power supply and function generator. A pulse of electricity having a particular amplitude variation or that includes a particular set of frequencies can be provided from the function generator to the piezoelectric element to impart a desired vibration to the substrate.
Thus, piezoelectric elements have been combined with support circuits including signal conditioning, energy harvesting, and signal generator circuits. Each of these support circuits includes a variety of electronic components, such as capacitors, resistors, inductors, transistors, memories, integrated circuits, batteries, transmitters, and the like. These components have typically been mounted and wired together on a printed circuit board. The piezoelectric elements and the printed circuit board have been separately mounted on the substrate and wiring provided there between.
Commercially available piezoelectric composites have been constructed from a piezoelectric element composed of an array of parallel fibers of a piezoelectric material. The piezoelectric element has been sandwiched between two sheets of metalized polyimide, as described in U.S. Pat. No. 6,629,341 to Wilkie, et al. (“the '341 patent”), incorporated herein by reference. One of the sheets of polyimide has a pair of metal pads on a top surface in electrical contact with metalization layers on inner surfaces of the polyimide sheets contacting each surface of the piezoelectric element. Wiring has been connected to the pair of contact pads extending to the printed circuit board carrying the support circuits.
Providing piezoelectric composites and circuit boards with support circuits, mounting them on a substrate, and connecting the piezoelectric composites to their support circuits has posed difficulties, and a system has not yet been optimized for this purpose. Thus, an improved system is needed, and this system is provided in the present patent application.